Head mounted display and method for controlling the same

ABSTRACT

A head mounted display (HMD) configured to provide a surrounding image is disclosed. The HMD includes a display unit configured to display a section of the surrounding image corresponding to a front direction of the HMD, a first sensor group including at least one sensor configured to sense motion of the HMD, a second sensor group including at least one sensor provided to the HMD to capture a circumjacent image, and a processor configured to control the display unit, the first sensor group and the second sensor group to acquire first sensing information from the first sensor group and second sensing information from the second sensor group, wherein the processor detects a state of the HMD using at least one of the first sensing information and the second sensing information, the state of the HMD including a static state in which an absolute position of the HMD does not change and a moving state in which the absolute position changes, detects, when the state of the HMD is detected as the static state, a direction in which a front of the HMD faces based on the first sensing information or on the first sensing information and the second sensing information, detects, when the state of the HMD is detected as the moving state, the direction in which the front of the HMD faces based on the second sensing information or based on the second sensing information and the corrected first sensing information, and displays an image of a section of the surrounding image corresponding to the detected direction.

Pursuant to 35 U.S.C. §119(a), this application claims the benefit ofKorean Patent Application No. 10-2014-0049194, filed on Apr. 24, 2014,which is hereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a head mounted display (HMD)configured to provide a surrounding image and a method for controllingthe same, more particularly, to a method for controlling activation ofsensor groups depending upon whether the HMD is in a static state or amoving state to more accurately sense rotation of the head of a userwearing the HMD and to display a surrounding image corresponding to thesensed rotation.

2. Discussion of the Related Art

A head mounted display (HMD) is a wearable device that is worn on thehead like eye glasses to receive various kinds of information. With thetrend toward more lightweight and compact digital devices, variouswearable devices have been developed and HMDs have also been widelyused. An HMD may not only function as a display, but also provide userswith various services by combining augmented reality and N-screentechnology.

Particularly, the HMD may provide a surrounding image to provide a morerealistic virtual space to the user. Herein, the surrounding image mayrepresent visual information unfolded around the HMD in all directions.Accordingly, the HMD may detect the direction in which the face of theuser wearing the HMD is oriented and display an image of a section ofthe surrounding image corresponding to the detected direction. Thereby,the user may feel as if he/she is actually present in the virtual space.

However, in the case that the user wearing the HMD receives thesurrounding image while moving, the HMD may fail to accurately senserotation of the user's head, accordingly the HMD may perform anincorrect operation counter to the user's intention.

SUMMARY OF THE INVENTION

Accordingly, the present disclosure is directed to an HMD and a controlmethod for the same which substantially obviate one or more problems dueto limitations and disadvantages of the related art.

An object of the present disclosure is to provide an HMD configured todetect the static state or moving state of the HMD and to controlactivation of sensor groups according to the detected state and a methodof controlling the same.

Another object of the present disclosure is to provide an HMD configuredto detect, in the case that the HMD is in the static state, thedirection in which the front of the HMD faces using sensing informationacquired from the respective sensor groups and a method of controllingthe same.

Another object of the present disclosure is to provide an HMD configuredto correct, in the case that the HMD is in the moving state, sensinginformation acquired from a sensor group and detect the direction inwhich the front of the HMD faces using the corrected sensing informationand a method of controlling the same.

Another object of the present disclosure is to provide an HMD configuredto set, in the case that the front direction of the HMD is detected inthe moving state, a reference image and a method of controlling thesame.

Another object of the present disclosure is to provide an HMD configuredto receive travel information from an external device to correct sensinginformation and a method of controlling the same.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, ahead mounted display (HMD) configured to provide a surrounding imageincluding a display unit configured to display a section of thesurrounding image corresponding to a front direction of the HMD, a firstsensor group including at least one sensor configured to sense a motionof the HMD, a second sensor group including at least one sensorproviding the HMD to capture a circumjacent image, and a processorconfigured to control the display unit, the first sensor group and thesecond sensor group to acquire first sensing information from the firstsensor group and second sensing information from the second sensorgroup, wherein the processor is further configured to detect a state ofthe HMD using at least one of the first sensing information and thesecond sensing information, the state of the HMD including a staticstate in which an absolute position of the HMD does not change and amoving state in which the absolute position changes, detect, when thestate of the HMD is detected as the static state, a direction in which afront of the HMD faces based on the first sensing information or basedon the first sensing information and the second sensing information,detects, when the state of the HMD is detected as the moving state, thedirection in which the front of the HMD faces based on the secondsensing information or based on the second sensing information and thecorrected first sensing information, and display an image of a sectionof the surrounding image corresponding to the detected direction.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a block diagram illustrating a head mounted display (HMD)according to the present disclosure;

FIG. 2 is a view illustrating an HMD providing a surrounding imageaccording to one embodiment;

FIGS. 3A and 3B are views illustrating detection of the moving state ofthe HMD according to one embodiment;

FIG. 4A is a view illustrating the HMD setting a first reference imageaccording to one embodiment;

FIG. 4B is a view illustrating the HMD detecting the front direction ofthe HMD using the first reference image according to one embodiment;

FIG. 5A is a view illustrating the HMD setting a second reference imageaccording to one embodiment;

FIG. 5B is a view illustrating the HMD detecting the front direction ofthe HMD using the second reference image according to one embodiment;

FIGS. 6A and 6B are views illustrating the HMD correcting the firstsensing information and detecting the front direction thereof using thecorrected first sensing information and the second sensing informationaccording to one embodiment; and

FIG. 7 is a flowchart illustrating a method of controlling the HMD.

DETAILED DESCRIPTION OF THE INVENTION

Although the terms used in this specification are selected, as much aspossible, from general terms that are widely used in the art at presentwhile taking into consideration of functions of the elements, theseterms may be replaced by other terms according to intentions of thoseskilled in the art, customs, emergence of new technologies, or the like.In addition, in a specific case, terms that are arbitrarily selected bythe applicant may be used. In this case, meanings of these terms may bedisclosed in corresponding parts of this specification. Accordingly, itshould be noted that the terms used herein should be construed based onpractical meanings thereof and the whole content of this specification,rather than being simply construed based on names of the terms.

Reference will now be made in detail to the preferred embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.However, the scope of the present disclosure is not limited to theillustrated embodiments.

FIG. 1 is a block diagram illustrating a head mounted display (HMD)according to the present disclosure. As shown in FIG. 1, the HMD mayinclude a display unit 1020, a communication unit 1030, a first sensorgroup 1040, a second sensor group 1050 and a processor 1010. Accordingto one embodiment, some of the constituents shown in FIG. 1 may not beemployed and a new constituent may be added, when desired by a personskilled in the art.

The display unit 1020 may display an image. Herein, the image mayrepresent visual information visually recognizable by a user, which mayinclude pictures, photos, text, moving images, videos, an executionwindow of an application, etc. Particularly, in the present disclosure,the display unit 1020 may display a circumjacent image. Herein, thesurrounding image may represent an unfolded image shown in alldirections (e.g., front, rear, left, right, up and down directions)around the HMD. Particularly, the processor 1010 may detect thedirection in which the user's face is oriented and provide a surroundingimage corresponding to this direction. Thereby, the HMD may provide theuser with a more realistic virtual environment.

The communication unit 1030 may perform communication with an externaldevice based on various protocols to transmit/receive data. In addition,the communication unit 1030 may access a wired or wireless network totransmit/receive digital data such as content. For example, thecommunication unit 1030 may use communication standards WLAN (WirelessLAN), Wi-Fi, WiBro (Wireless broadband), WiMAX (World Interoperabilityfor Microwave Access), and HSDPA (High Speed Downlink Packet Access) toaccess a wireless network. According to one embodiment of the presentdisclosure, the external device may be a means of transportation (e.g. avehicle). A related example will be described in detail below.

The first sensor group 1040 may represent a group of sensors which sensemotion of the HMD. More specifically, the first sensor group 1040 maypresent a group of sensors which sense position, action, rotation andmovement of the HMD. Accordingly, the first sensor group 1040 mayinclude at least one sensor configured to sense a motion of the HMD. Forexample, the first sensor group 1040 may include at least one of anacceleration sensor, a gyro sensor, a geomagnetic sensor, a globalpositioning system (GPS) sensor, a pressure sensor, an elevation sensorand a proximity sensor. In addition, the first sensor group 1040 mayinclude various other sensors for sensing a motion of the HMD.

The sensor(s) included in the first sensor group 1040 may besimultaneously activated or deactivated by a control signal from theprocessor 1010. When activated, the first sensor group 1040 may transmitthe result of sensing of a motion of the HMD to the processor 1010 asfirst sensing information. Upon receiving the first sensing information,the processor 1010 may detect the motion of the HMD to perform variouscontrol operations.

The second sensor group 1050 may represent a group of sensors forcapturing an image of surroundings of the HMD. Accordingly, the secondsensor group 1050 may include at least one sensor for capturing acircumjacent image of the HMD. For example, the second sensor group 1050may include at least one of a camera sensor, an infrared sensor and aproximity sensor.

The sensor(s) included in the second sensor group 1050 may besimultaneously activated or deactivated by a control signal from theprocessor 1010. When activated, the second sensor group 1050 maytransmit the result of capturing the circumjacent image of the HMD tothe processor 1010 as the second sensing information. Upon receiving thesecond sensing information, the processor 1010 may detect thecircumjacent image of the HMD to perform various control operations.

The first sensor group 1040 and the second sensor group 1050 may sharethe same sensor. In addition, the first sensor group 1040 and the secondsensor group 1050 may be activated simultaneously or respectively by theprocessor 1010.

The processor 1010 may control each of the units of the HMD and alsocontrol transmission/reception of data or information between the units.In addition, the processor 1010 may process data in the HMD to executevarious applications. In addition, the processor 1010 may controlcontent executed in the HMD based on a control command.

More specifically, the processor 1010 may provide a surrounding imageusing the display unit 1020. Herein, the surrounding image may representan image unfolded in all directions (e.g., front, rear, left, right, upand down directions) around the HMD, as described above. The processor1010 may detect the direction in which the user's face is oriented anddisplay an image of a section of a surrounding image corresponding tothe direction of the face. Thereby, the processor 1010 may enable theuser feel present in a virtual space provided by the surrounding image.

At this time, to accurately detect the direction in which the user'sface is oriented, the processor 1010 uses first sensing informationacquired from the first sensor group 1040 and second sensing informationacquired from the second sensor group 1050. First, the processor 1010may detect whether the state of the HMD is a static state, in which theabsolute position of the user does not change, or a moving state, inwhich the absolute position of the user changes, using the first sensinginformation and/or the second sensing information. The processor 1010may control activation of the first sensor group 1040 and the secondsensor group 1050 according to the detected static state or movingstate, thereby detecting the orientation of the user's face and/or thedegree of rotation of the user's head, which will be described in detaillater.

In the case that the processor 1010 detects the direction of the user'sface, the processor 1010 may display an image of a section of asurrounding image corresponding to the direction of the face. At thistime, the processor 1010 may display the surrounding image using varioustechniques. According to one embodiment, the processor 1010 may displaythe image with a see-through technique. The see-through techniquerepresents a technique of allowing the user wearing an HMD to recognizean image displayed on a transparent display panel while recognizing acircumjacent environment. According to another embodiment, the processor1010 may display an image with a front-light technique. The front-lighttechnique represents a technique of displaying an image through an imagerather than directly projecting light onto the user's eyes. According toanother embodiment, the processor 1010 may display an image with asee-closed technique. The see-closed technique represents a technique ofallowing the user wearing an HMD to recognize an image displayed on anopaque display panel without recognizing a circumjacent environment.

Hereinafter, it will be assumed that the processor 1010 displays animage with the see-closed technique. The present disclosure is notlimited to this embodiment. The see-through technique and thefront-light technique are also applicable to the embodiments discussedbelow.

In the description given below, it will be assumed that the process ofgenerating and receiving a signal according to sensing information,which will not be repeatedly described, is included in the case thateach step or operation performed by the HMD begins with the sensinginformation. In addition, the processor 1010 may be described ascontrolling the HMD or at least one unit included in the HMD accordingto the sensing information, and may also be referred as a device.

In the block diagram of FIG. 1 illustrating a device according to oneembodiment, the separately indicated blocks represent hardware units ofthe device which are logically distinguished from each other.Accordingly, the hardware units of the device may be installed as onechip or plural chips according to design of the device.

FIG. 2 is a view illustrating an HMD providing a surrounding imageaccording to one embodiment;

In the present disclosure, the HMD 2040 may provide a surrounding image.Herein, the surrounding image is an image unfolded in all directionsaround the HMD 2040, as mentioned above. Accordingly, the HMD 2040 mayprovide a surrounding image corresponding to various directions such asup, down, left, right, front and rear directions. Otherwise, the HMD2040 may provide a surrounding image corresponding to various directionsincluding horizontal, vertical, and diagonal directions. However, thesurrounding image is not limited to the image unfolded in alldirections. It includes an image unfolded only in the front-reardirection, left-right direction, up-down direction, vertical direction,horizontal direction, or diagonal direction.

The HMD 2040 may detect the direction of the user's face and provide animage of a section of a surrounding image corresponding to thisdirection. In the present disclosure, the HMD 2040 may indirectly detectthe direction of the user's face by detecting the direction in which thefront of the HMD 2040 is oriented since the HMD 2040 is a wearabledevice worn on the user's face. Since the direction in which the user'sface is oriented is indirectly detected by detecting the direction inwhich the front of the HMD 2040 is oriented, there may be a certainerror between those two directions. For example, in the case that avehicle turns left or right while the user riding thereon gazes at asurrounding image, the HMD 2040 may recognize that the front directionof the HMD 2040 has changed even though the user's head has not rotated.Herein, rotation of the user's head may represent a case in which onlythe user's face rotates with the user's body fixed (or not rotating). Inthis case, the HMD 2040 may perform an incorrect operation of providinga surrounding image corresponding to the direction changed differentlyfrom the user's intention.

To prevent such incorrect operation, the HMD 2040 may first detect thestate of the HMD 2040. Herein, the state of the HMD 2040 may include astatic state in which the absolute position of the HMD 2040 does notchange and a moving state in which the absolute position of the I-IMD2040 changes. More specifically, the state of the HMD 2040 may include astatic state in which the absolute position of the HMD 2040 is“substantially” unchanged and a moving state in which the absoluteposition of the HMD 2040 “substantially” changes. Whether the absoluteposition of the HMD 2040 “substantially” changes may be determined basedon a threshold distance. For example, in the case that the absoluteposition of the HMD 2040 changes by a distance less than or equal to athreshold distance for a predetermined time, the HMD 2040 may detect thestate of the HMD 2040 as the static state. On the other hand, in thecase that the absolute position of the HMD 2040 changes by a distancegreater than a threshold distance for the predetermined time, the HMD2040 may detect the state of the HMD 2040 as the moving state. Herein,the threshold distance may be set to various values by the method ofmanufacturing the HMD 2040, the type of an executed application, theuser, and the like.

The state of the HMD 2040 may be detected using at least one of theaforementioned first sensor group and second sensor group. In otherwords, the state of the HMD 2040 may be detected using the first sensinginformation, which is a result of sensing by the first sensor group,and/or the second sensing information, which is a result of sensing bythe second sensor group.

According to one embodiment, in detecting the state of the HMD 2040using the first sensing information, the HMD 2040 may acquireinformation about the absolute position of the HMD 2040 as the firstsensing information using a GPS sensor included in the first sensorgroup. The HMD 2040 may receive information about the absolute positionof the HMD 2040 in real time using the GPS sensor and detect whether theHMD 2040 moves by a distance less than or equal to the thresholddistance or a distance greater than the threshold distance for thepredetermined time, thereby detecting the state of the HMD 2040.

According to another embodiment, in detecting the state of the HMD 2040using the second sensing information, the HMD 2040 the HMD 2040 maydetect the state of the HMD 2040 by processing an acquired surroundingimage using the second sensor group. More specifically, the HMD 2040 maycapture a circumjacent image of the HMD 2040 as the second sensinginformation using the second sensor group. Furthermore, the HMD 2040 mayprocess the captured circumjacent image and detect the state of the HMD2040 base on the result of processing. For example, in the case that thecircumjacent image is changed beyond a predetermined ratio for apredetermined time, the HMD 2040 may detect that the absolute positionof the HMD 2040 has substantially changed, and thus detect the state ofthe HMD 2040 as the moving state.

In another embodiment, the HMD 2040 may detect the state of the HMD 2040by acquiring sensing information from an external device using acommunication unit. In the case that the external device is a means oftransportation (vehicle) that the user may ride, the device may detectthe state of the HMD 2040 by performing communication with the externaldevice. For example, in the case that the external device travels at aspeed greater than a predetermined speed, the external device maytransmit travel information related to traveling to the HMD 2040. Whenthe HMD 2040 receives such travel information, it may detect change ofthe absolute position of the HMD 2040 based on the travel informationand detect the state of the HMD 2040 based on the detected change of theabsolute position of the HMD 2040.

In the case that the HMD 2040 detects the static state of the HMD 2040through one or a combination of the aforementioned embodiments, the HMD2040 may control activation of the first sensor group and the secondsensor group. According to one embodiment, when the HMD 2040 detects thestatic state of the HMD 2040, the HMD 2040 may activate the first sensorgroup or maintain activation of the first sensor group. At this time,the HMD 2040 may deactivate the second sensor group. Further, the HMD2040 may acquire the first sensing information and detect the directionin which the front of the HMD 2040 faces, based on the acquired firstsensing information. For example, the HMD 2040 may detect the directionand/or degree of rotation of the HMD 2040 using a gyro sensor and/or anacceleration sensor included in the first sensor group, and detect thedirection in which the front of the HMD 2040 is oriented, based on thedetected direction and degree of rotation. Since the absolute positionof the HMD 2040 is static, an error between the front direction of theHMD 2040 and the direction in which the user's face is oriented is notgreat even though only the first sensor group is used.

According to another embodiment, in the case that the HMD 2040 detectsthe static state of the HMD 2040, the HMD 2040 may simultaneouslyactivate the first sensor group and the second sensor group or maintainactivation of the first sensor group and the second sensor group.Further, the HMD 2040 may acquire the first sensing information from theactivated first sensor group and the second sensing information from thesecond sensor group, and then detect the direction in which the front ofthe HMD 2040 faces, based on the acquired first sensing information andsecond sensing information. For example, the HMD 2040 may detect thedirection and/or degree of rotation of the HMD 2040 using a gyro sensorand/or an acceleration sensor included in the first sensor group andprocess a circumjacent image using a camera sensor included in thesecond sensor group, thereby detecting the direction in which the frontof the HMD 2040 is oriented. Unlike the previous embodiment, the HMD2040 of this embodiment uses the second sensor group in addition to thefirst sensor group, and therefore may detect the direction of the frontof the HMD 2040 more accurately and rapidly.

In the case that the HMD 2040 detects the moving state of the HMD 2040through one or a combination of the aforementioned embodiments, the HMD2040 may also control activation of the first sensor group and thesecond sensor group. A detailed description of this embodiment will begiven below with reference to FIGS. 3A to 6B.

When the HMD 2040 detects the direction in which the front of the HMD2040 faces, it may display an image of a section of a surrounding imagecorresponding to the detected direction. For example, in the case thatthe HMD 2040 detects that the front of the HMD 2040 faces in a firstdirection, as shown in the figures, the HMD 2040 may display a firstimage 2010 corresponding to the first direction. At this time, in thecase that leftward rotation of the HMD 2040 by 90° is detected, the HMD2040 may display a second image 2020 corresponding to this direction ofrotation. Herein, the second image 2020 may be a partial image includedin the surrounding image. In the case that rightward rotation of the HMD2040 by 90° is detected, the HMD 2040 may display a third image 2030corresponding to this direction of rotation. Herein, the third image2030 may be a partial image included in the surrounding image.

FIGS. 3A and 3B are views illustrating detection of the moving state ofthe HMD according to one embodiment.

The HMD 3010 in the moving state detects only a motion of the HMD 3010,and thus it is difficult form the HMD 3010 to accurately detect rotationof the head of the user 3020. In other words, the HMD 3010 in the movingstate uses only the first sensor group configured to detect the motionof the HMD 3010, and thus may not accurately detect rotation of the headof the user 3020.

In the case that only the first sensor group is used, the HMD 3010detects only the motion of the HMD 3010, and thus it may detect that thehead of the user 3020 has rotated, even when the head of the user 3020does not rotate, but the body of the user 3020 rotates. Herein, rotationof the head may represent the case in which only the face of the user3020 rotates without rotation of the body of the user 3020. Accordingly,in this case, the HMD 3010 may use only the second sensor groupconfigured to capture a circumjacent image in place of the first sensorgroup configured to sense motion of the HMD 3010, or may use both thefirst sensor group and the second sensor group to detect rotation of thefront of the HMD 3010. Accordingly, it may detect rotation of the headof the user 3020 more accurately. Thereby, incorrect operation of theHMD 3010 may be prevented.

More specifically, in the case that the moving state of the HMD 3010 isdetected using the embodiment illustrated in FIG. 2, the HMD 3010 maydetect activation of the first sensor group and the second sensor group.According to one embodiment, upon detecting the moving state of the HMD3010, the HMD 3010 may activate the second sensor group or maintainactivation of the second sensor group. At this time, the HMD 3010 maydeactivate the first sensor group. Further, the HMD 3010 may acquire thesecond sensing information from the activated second sensor group anddetect the direction in which the front of the HMD 3010 faces, based onthe acquired second sensing information. For example, the HMD 3010 maycapture a circumjacent image of the HMD 3010 using a camera sensorincluded in the second sensor group and compare the capturedcircumjacent image with a predetermined image or a reference image.Thereby, the direction in which the front of the HMD 3010 faces may bedetected. A detailed description will be given later with reference toFIGS. 4A to 5B.

According to another embodiment, when the moving state of the HMD 3010is detected, the HMD 3010 may activate the first sensor group and thesecond sensor group or maintain activation of the first sensor group andthe second sensor group. Further, the HMD 3010 may acquire first sensinginformation and second sensing information respectively from theactivated first sensor group and second sensor group, and the directionin which the front of the HMD 3010 faces, based on the acquired firstsensing information and second sensing information. Since the firstsensing information may involve a certain error as described above, theHMD 3010 may correct the first sensing information and detect thedirection in which the front of the HMD 3010 faces, based on thecorrected first sensing information. For example, the HMD 3010 mayacquire a circumjacent image as the second sensing information, usingthe camera sensor included in the second sensor group. In addition, theHMD 3010 may acquire motion of the HMD 3010 as the first sensinginformation, using a sensor included in the first sensor group. Since acertain error may be produced in the first sensing information indetecting rotation of the head of the moving user 3020, the HMD 3010 maycorrect the acquired first sensing information. At this time, the HMD3010 may use the communication unit to acquire information forcorrection of the first sensing information from the external device3030, as will be described in detail later with reference to FIGS. 6Aand 6B. The HMD 3010 may detect the direction in which the front of theHMD 3010 faces, using the acquired second sensing information and thecorrected first sensing information. Thereby, the orientation of thehead of the user 3020 may be indirectly detected.

A detailed description will be given below of operation of the HMD 3010performed in the case that the user 3020 in a traveling vehicle as shownin FIG. 3A is provided with surrounding images 3040, 3050 and 3060through the HMD 3010. Particularly, a detailed description will be givenof the case in which the car 3030 turns left with the user 3020 ridingthereon.

For example, in the case that a passenger gazes in the front directionas shown in FIG. 3B, the HMD 3010 may display a first image 3040 of thesurrounding images 3040, 3050 and 3060 corresponding to the frontdirection. In the case that the car 3030 turns during traveling, thedisplayed surrounding image 3040, 3050 and 3060 may vary according to anactivated sensor group to detect rotation of the head of the user 3020.In the case that the car 3030 turns left by 45° and rotation of the headof the user 3020 is detected using only the first sensor group, the HMD3010 may detect that the front of the HMD 3010 has been rotated 45°leftward by rotation of the car 3030. In other words, the HMD 3010 maydetect that the user 3020 wearing the HMD 3010 has turned their headleftward by 45°. As a result, the HMD 3010 may display a second image3050 corresponding to the direction rotated 45° leftward. Further, asshown in FIG. 3B, in the case that the car 3030 is rotated 90° bycompleting turning left (FIG. 3B-(3)), the HMD 3010 may detect that theHMD 3010 has rotated 90° leftward, and thus display a third image 3060corresponding to this rotated direction.

This operation of the HMD 3010 may be counter to the intention of theuser 3020. It is more probable that the moving user 3020 does not turntheir whole body but rather simply turns the head with the bodysubstantially not rotated, as intended to see an image in the leftdirection or right direction. Accordingly, as described above, changingthe images by detecting rotation of the whole body with the first sensorgroup may counter to the intention of the user 3020. In the presentdisclosure, in the case that the HMD 3010 detects the moving state ofthe HMD 3010, the HMD 3010 uses the second sensing information alone orthe corrected first sensing information and the second sensinginformation to detect rotation of the user 3020. Thereby, theaforementioned incorrect operation of the HMD 3010 may be prevented.

Accordingly, the HMD 3010 of the present disclosure may maintain thefirst image 3040 corresponding to the front direction even when thevehicle turns left by 45° or 90°.

Hereinafter, a detailed description will be given of embodiments inwhich the HMD 3010 in the moving state detects the front direction ofthe HMD 3010 using the second sensing information or using the correctedfirst sensing information and the second sensing information. Morespecifically, an embodiment of the HMD 3010 detecting the frontdirection using only the second sensing information will be described indetail with reference to FIGS. 4A and 5B. In addition, anotherembodiment of the HMD 3010 detecting the front direction using thecorrected first sensing information and the second sensing informationwill be described with reference to FIGS. 6A and 6B.

When the HMD 3010 detects the moving state, it may activate the secondsensor group or maintain activation of the second sensor group. At thistime, the HMD 3010 may deactivate the first sensor group. The HMD 3010may acquire the second sensing information and detect the frontdirection of the HMD 3010 using the acquired second sensing information.

To detect the front direction of the HMD 3010 or the direction of thehead of the user 3020 using the second sensing information, the HMD 3010may pre-detect whether a current space containing the user 3020 is anopen space or a closed space. Depending upon whether the current spaceis an open space or a closed space, the HMD 3010 may acquire the secondsensing information in different manners. For example, the method ofdetecting the front direction of the HMD 3010 using the second sensinginformation may differ between the case in which the user 3020 travelsin the car 3030 and the case in which the user 3020 walks.

Accordingly, in the case that the HMD 3010 in the moving state detectsthe front direction using the second sensing information, the HMD 3010may detect the type of the space in which the MID 3010 is contained. Atthis time, the HMD 3010 may detect the type of the space containing theHMD 3010 through various embodiments. According to one embodiment, theHMD 3010 may detect the type of the space containing the HMD 3010 bymatching a circumjacent image of the HMD 3010 with a predeterminedimage.

For example, in the case that the HMD 3010 stores an internal image ofthe vehicle as the predetermined image, the HMD 3010 may capture acircumjacent image using the second sensor group and match the capturedcircumjacent image with the predetermined image. At this time, upondetecting that the captured image matches the circumjacent image withina ratio greater than a predetermined ratio, the HMD 3010 may detect thespace containing the HMD 3010 as a closed space. On the other hand, upondetecting that the captured image and the circumjacent image match aratio less than or equal to the predetermined, the HMD 3010 may detectthe space containing the HMD 3010 as an open space. According to anotherembodiment, the HMD 3010 may acquire a circumjacent image as the secondsensing information using the camera sensor included in the secondsensor group and process the circumjacent image to detect the type ofthe space containing the HMD 3010. Alternatively, in the case that theuser 3020 wearing the HMD 3010 rides in an external device, the HMD 3010may perform communication with the external device to detect the type ofthe space containing the HMD 3010. The HMD 3010 may detect the type ofthe space containing the HMD 3010 through various embodiments and thedetection operation is not limited to the described embodiments.

Hereinafter, a detailed description will be given of a method for theHMD 3010 to detect the front direction of the HMD 3010 after detectingthe closed space or open space according to the described embodiments.

FIG. 4A is a view illustrating the HMD setting a first reference imageaccording to one embodiment;

In the case that the closed space is detected through the embodimentsdescribed above, the HMD 4010 may set a first reference image 4020. Morespecifically, upon detecting the closed space, the HMD 4010 may set acircumjacent image in a first direction as the first reference image4020 using the second sensor group. Herein, the first direction may beset to be various directions such as front, rear, up, down, left, rightand diagonal directions. For example, in the case that the HMD 4010detects the closed space and this closed space is the interior of thevehicle, the HMD 4010 may set an image of the driver's seat in the frontdirection of the HMD 4010 as the first reference image 4020, as shown inFIG. 4A.

This is intended to accurately detect rotation of the user's head bysetting the image of the closed space as the first reference image 4020and matching the first reference image 4020 with a captured circumjacentimage in real time. A detailed description of the HMD 4010 detectingrotation of the user's head or the front direction of the HMD 4010 usingthe first reference image 4020 will be given below with reference toFIG. 4B.

As described above, in the case that the HMD 4010 detects a closedspace, the HMD 4010 may reset the image of the closed space as the firstreference image 4020. However, in another embodiment, the firstreference image 4020 may be preset before the closed space is detected.For example, in the case that the closed space is detected when thepredetermined image matches the circumjacent image as described above,the HMD 4010 may set the predetermined image to the first referenceimage 4020. In addition, the user may set an internal image of afrequently encountered living space such as home and a car as the firstreference image 4020.

FIG. 4B is a view illustrating the HMD detecting the front direction ofthe HMD using the first reference image according to one embodiment.

In the case that the first reference image 4020 is set through theembodiment related to FIG. 4A, the HMD 4010 may detect the frontdirection of the HMD 4010 by matching the first reference image 4020with a circumjacent image in real time. More specifically, the HMD 4010may acquire a circumjacent image using at least one sensor included inthe second sensor group and compare the acquired circumjacent image withthe first reference image 4020 in real time. Alternatively, the HMD 4010may compare the acquired circumjacent image with the first referenceimage 4020 at predetermined time intervals. The HMD 4010 may detect thematching sections of the first reference image 4020 and the circumjacentimage, the position of the matching sections and/or the degree ofmatching, thereby detecting the direction in which the front of the HMD4010 faces.

For example, in the case that a section of the circumjacent imagedetected in real time matches a left section 4020-1 of the firstreference image 4020, the HMD 4010 may detect that the front of the HMD4010 has rotated leftward. In the case that a section of thecircumjacent image detected in real time matches a right section 4020-2of the first reference image 4020, the HMD 4010 may detect that thefront of the HMD 4010 has rotated rightward. In this case, the HMD 4010may display an image in the surrounding image corresponding to thedetected direction.

In the case that an internal image of a transport means (e.g., a car ora train) is set as the first reference image 4020, the HMD 4010 maydetect a variable image section 4030 of the first reference image 4020which is changeable. For example, in the case that the internal image ofa car is set as the first reference image 4020, the HMD 4010 may detecta window image 4030 in the internal image of the car as the variableimage. Thereby, the HMD 4010 may detect the window image by processingthe internal image of the car.

At this time, in matching the first reference image 4020 with acircumjacent image, the HMD 4010 may match the first reference image4020 other than the detected section of the variable image with thecircumjacent image. This is because the window image of the car mayconsistently change due to movement of the car. In the case that thefirst reference image 4020 including the variable image matches acircumjacent image in real time, the HMD 4010 may perform the matchingoperation even for the unnecessary section, and accordingly the matchingoperation may take a long time and matching accuracy may be lowered,thereby increasing the possibility of incorrect operation. Accordingly,the HMD 4010 may detect a variable image in the first reference image4020 and thus perform matching with the circumjacent image moreefficiently.

FIG. 5A is a view illustrating the HMD setting a second reference imageaccording to one embodiment.

In the case that the open space is detected through the embodimentsdescribed above, the HMD 5010 may set a second reference image 5020.More specifically, upon detecting the open space, the HMD 5010 may set acircumjacent image in a second direction as the second reference image5020 using the second sensor group. Herein, the second reference image5020 may be an image of the user's body. Accordingly, the seconddirection may represent the downward direction of the HMD 5010. Forexample, when the HMD 5010 detects an open space for example, in thecase that the user wearing the HMD 5010 walks along a street, the HMD5010 may set an image (e.g., a shoulder image) of the user's bodypositioned below the HMD 5010 as the second reference image 5020.

This is intended to accurately detect rotation of the user's head withrespect to the user's body by setting the image of the user's body asthe second reference image 5020 and matching the second reference image5020 with a captured circumjacent image in real time. A detaileddescription of the HMD 5010 detecting rotation of the user's head or thefront direction of the HMD 5010 using the second reference image 5020will be given below with reference to FIG. 5B.

The second reference image 5020 may be set before the open space isdetected. A relevant detailed description has been given above withreference to FIG. 4A.

Meanwhile, the HMD 5010 may set the first reference image in the firstdirection and the second reference image 5020 in the second directionusing the same camera sensor included in the second sensor group. Atthis time, the HMD 5010 may rotate the camera sensor from the firstdirection to the second direction to acquire the second reference image5020. Alternatively, the HMD 5010 may set the first reference image andthe second reference image 5020 respectively using plural camera sensorsfacing in the first direction and the second direction respectively.

FIG. 5B is a view illustrating the HMD detecting the front direction ofthe HMD using the second reference image according to one embodiment.

When the second reference image 5020 is set through the embodimentdescribed with relation to FIG. 5A, the HMD 5010 may detect the frontdirection of the HMD 5010 by matching the second reference image 5020with a circumjacent image 5030-1, 5030-2 in real time. Morespecifically, the HMD 5010 may acquire a circumjacent image 5030-1,5030-2 using at least one sensor included in the second sensor group,and compare the acquired circumjacent image 5030-1, 5030-2 with thesecond reference image 5020. Alternatively, the HMD 5010 may compare theacquired circumjacent image 5030-1, 5030-2 with the second referenceimage 5020 for predetermined time intervals. The HMD 5010 may detect themutual matching sections of the second reference image 5020 and thecircumjacent image 5030-1, 5030-2, the position of the matching sectionsand/or the degree of matching, thereby detecting the direction in whichthe front of the HMD 5010 faces.

For example, in the case that a section of the circumjacent image 5030-1detected in real time matches a left section of the second referenceimage 5020, the HMD 5010 may detect that the front of the HMD 5010 hasrotated leftward. In the case that a section of the circumjacent image5030-2 detected in real time matches a right section of the secondreference image 5020, the HMD 5010 may detect that the front of the HMD5010 has rotated rightward. In this case, the HMD 5010 may display animage in the surrounding image corresponding to the detected direction.

In the case that an image of the user's body is set as the secondreference image 5020, a variable image section (not shown) of the secondreference image 5020 which is changeable. For example, an image capturedin the downward direction of the HMD 5010 is set as the second referenceimage 5020, the HMD 5010 may detect the image other than the image ofthe user's body as the variable image. Upon detecting the variableimage, the HMD 5010 may match the second reference image 5020 other thanthe section of the variable image with the circumjacent image. Arelevant detailed description has been given above with reference toFIG. 4B.

FIGS. 6A and 6B are views illustrating the HMD correcting the firstsensing information and detecting the front direction thereof using thecorrected first sensing information and the second sensing informationaccording to one embodiment.

As shown in FIG. 6A, the user wearing the HMD 6020 may ride in a meansof transportation 6010. At this time, the user's head may rotate at thesame time as the means of transportation 6010 rotates. In the case thatthe HMD 6020 detects the front direction of the HMD 6020 using the firstsensing information which has not been corrected, there may be a certainerror between the detected front direction of the HMD 6020 and theactual direction of the user's head. That is, in the case that the firstsensing information is used without being corrected, the HMD 6020 mayacquire, as the first sensing information, information including boththe degree of rotation of the means of transportation and the degree ofrotation of the user's head, using the first sensor group. Morespecifically, in this case, the HMD 6020 may acquire, as the firstsensing information, information combining the degree of rotation of themeans of transportation 6010 and the degree of rotation of the user'shead, using the first sensing group.

For example, as shown in FIG. 6A, in the cast that the car 6010 on whichthe user rides turns left by 45° and the user rotates the head 90°leftward, the HMD 6020 may detect that the front of the HMD 6020 hasrotated 135° leftward. That is, in the case that the front direction ofthe HMD 6020 is detected using only the first sensor group, theinformation combining the degree of rotation of the car 6010 and thedegree of rotation of the user's head may be acquired as the firstsensing information. However, the actual degree of rotation of theuser's head corresponds to 90°, the sensing information detected by theHMD 6020 has an error. Accordingly, there is a need to correct the firstsensing information. Hereinafter, a detailed description will be givenof an embodiment in which the HMD 6020 corrects the first sensinginformation and detects the direction in which the front of the HMD 6020faces using both the corrected first sensing information and the secondsensing information.

According to one embodiment, the HMD 6020 may perform communication withan external device 6010 using a communication unit and correct the firstsensing information using the information received from the externaldevice 6010. Herein, the external device 6010 may be a means oftransportation 6010 which is capable of conducting communication. Forexample, the external device 6010 may be a car, an aircraft, a train, abicycle, and a motorcycle which are capable of conducting communication.

When the HMD 6020 detects the moving state of the HMD 6020, it mayactivate the first sensor group and the second sensor group or maintainactivation of the first sensor group and the second sensor group. TheHMD 6020 may acquire the first sensing information and the secondsensing information using the activated first sensor group and theactivated second sensor group respectively. Then, the HMD 6020 maycorrect the acquired first sensing information using informationreceived from the external device 6010. More specifically, the HMD 6020may receive, using a communication unit, third sensing informationsensed by the external device 6010 according to change of the absoluteposition of the external device 6010, and correct the first sensinginformation using the received third sensing information. Herein, thethird sensing information may represent the travel information about theexternal device 6010.

For example, in the case that the car turns left by 45° and the userrotates the head 90° leftward, the HMD 6020 may acquire, as the firstsensing information, information indicating that the front of the HMD6020 has rotated 135° leftward. At this time, the HMD 6020 may receive,as the third sensing information, the information indicating left turnof the car by 45° from the car 6010, using the communication unit. TheHMD 6020 may correct the first sensing information using the receivedthird sensing information. More specifically, the HMD 6020 may correctthe detected sensing value of 135° by the received sensing value of 45°.Accordingly, the HMD 6020 may detect that the front of the HMD 6020 hasrotated leftward by 90°, not 135°.

According to another embodiment, the HMD 6020 may correct the firstsensing information using the acquired second sensing information.

The HMD 6020 may detect the front direction of the HMD 6020 using thecorrected first sensing information and the second sensing information.In using the second sensing information, the method as described abovewith reference to FIGS. 4A to 5B or a method similar thereto may beapplied. The HMD 6020 may display an image of a section of a surroundingimage corresponding to the detected front direction of the HMD 6020.

FIG. 7 is a flowchart illustrating a method of controlling the HMD. Inthe flowchart, constituents similar or identical to those illustrated inFIGS. 1 to 6 will be not described in detail.

First, the HMD may detect the state of the HMD (S7010). Herein, thestate of the HMD may include a static state and a moving state. Thestatic state of the HMD may represent a state in which the absoluteposition of the HMD does not change. The moving state of the HMD mayrepresent a state in which the absolute position of the HMD changes.More specifically, the static state may represent a state in which theabsolute position of the HMD does not substantially change and themoving state may represent a state in which the absolute position of theHMD substantially changes. The HMD may detect the state of the HMD usinga first sensor group and/or a second sensor group, which has beendescribed above in detail with reference to FIG. 2.

In the case that the HMD detects the state of the HMD as the staticstate, the HMD may detect the direction in which the front of the HMDfaces based on the first sensing information or based on the firstsensing information and the second sensing information (S7020). In otherwords, in the case that the HMD detects the static state, the HMD maydetect the direction in which the front of the HMD faces, based on thefirst sensing information. Herein, the first sensing information mayrepresent sensing information acquired from an activated first sensorgroup. Alternatively, in the case that the HMD detects the static state,the HMD may detect the direction in which the front of the HMD faces,based on the first sensing information and the second sensinginformation. Herein, the second sensing information may representsensing information acquired from an activated second sensor group. Forexample, in the case that the first sensing information is used todetect the front direction, the HMD may detect the direction and degreeof rotation of the HMD using a gyro sensor included in the first sensorgroup, thereby detecting the front direction of the HMD. Alternatively,in the case that the second sensing information is used to detect thefront direction, the HMD may process a circumjacent image of the HMDusing a camera sensor included in the second sensor group, therebydetecting the front direction of the HMD. A detailed description hasbeen given above with reference to FIG. 2.

On the other hand, in the case that the HMD detects the moving state asthe state of the HMD, the HMD may detect the direction in which thefront of the HMD faces based on the second sensing information or on thesecond sensing information and the corrected first sensing information(S7030). In other words, in the case that the moving state of the HMD isdetected, the HMD may detect the direction in which the front of the HMDfaces based on the second sensing information. In this case, the HMD mayset a first reference image in a first direction or a second referenceimage in a second direction, and match the set first reference image orsecond reference image with a circumjacent image, thereby detecting thefront direction of the HMD. Herein, the first reference image and secondreference image may be set depending upon whether the space in which theHMD in the moving state is placed is a closed space or an open space,which has been described above in detail with reference to FIGS. 4A to5B. Alternatively, in the case that the moving state of the HMD isdetected, the HMD may detect the direction in which the front of the HMDfaces based on the second sensing information and the corrected firstsensing information. In this case, the HMD may receive third sensinginformation sensed by an external device according to change of theabsolute position of the external device, and correct the first sensinginformation using the received third sensing information. At this time,the HMD may use a communication unit capable of performing communicationwith the external device. A detailed description has been given abovewith reference to FIG. 6B.

Next, the HMD may display an image of a section of the surrounding imagecorresponding to the front direction of the HMD detected in a previousstep (S7020 or S7030) (S7040). Herein, the surrounding image mayrepresent an unfolded image shown in all directions (e.g., front, rear,left, right, up and down directions) around the HMD. In the case thatthe HMD detects that the front direction of the HMD is the firstdirection, the HMD may detect a first image corresponding to the firstdirection. Thereby, the HMD may enable the user wearing the HMD to feelpresent in a virtual space provided by the surrounding image.

Although descriptions have been given for the respective drawings forease of illustration, embodiments illustrated in the drawings may alsobe combined to implement a new embodiment. The scope of the presentdisclosure also covers designing a recording medium readable by acomputer having a program recorded to execute the described embodiments,as desired by those skilled in the art.

In addition, the HMD and a control method for the same according to thepresent disclosure are not limited to the described embodiments. Partsor all of the above embodiments can be selectively combined to producevarious variations.

As is apparent from the above description, the present disclosure haseffects as follows.

According to one embodiment, activation of sensor groups is controlledaccording to the state of the HMD to detect the front direction of theHMD. Accordingly, rotation of the user's head may be detected moreaccurately and the possibility of incorrect operation of the HMD may belowered.

According to another embodiment, the HMD activates all the sensor groupsfor detection of the front direction of the HMD in the case that the HMDis in the static state. Accordingly, change of the front direction ofthe HMD may be detected more accurately and quickly.

According to another embodiment, the HMD sets a reference image andcompare the set reference image with circumjacent images in real time.Accordingly, rotation of the user's head with respect to the user's bodymay be detected more accurately.

According to another embodiment, the HMD receives travel informationfrom an external device to correct sensing information. Accordingly, thesensing information may be corrected more accurately and thus thepossibility of incorrect operation of the HMD may be lowered.

Details of the effects have been disclosed in the descriptions givenabove.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the present disclosure.Thus, the present invention is intended to cover the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents. The variations should not beseparately understood from the spirit or prospect of the presentdisclosure.

In addition, the HMD and a control method for the same in the presentdisclosure may be implemented, as code readable by a processor providedto a network device, in a recording medium readable by the processor.The recording medium readable by the processor includes all kinds ofrecording devices configured to store data readable by the processor.Examples of the recording medium readable by the processor include ROMs,RAMs, magnetic tapes, floppy disks, and optical data storage devices.Examples also include implementation in the form of a carrier wave suchas transmission over the Internet. In addition, the recording mediumreadable by the processor may be distributed to computer systemsconnected over a network, and thus code readable by the processor may bestored and executed in a distributed manner.

In addition, in the present disclosure, the rotation angle and directionmay not only represent accurate values, but also include a substantialrotation angle and direction within a certain range. That is, therotation angle and direction of the present disclosure may represent asubstantial rotation angle and direction within a certain error range.

In this specification, both a product invention and a method inventionhave been described. The descriptions thereof may be supplementarilyapplicable, when necessary.

What is claimed is:
 1. A head mounted display (HMD) configured toprovide a surrounding image, the HMD comprising: a display unitconfigured to display a section of the surrounding image correspondingto a front direction of the HMD; a first sensor group comprising atleast one sensor configured to sense a motion of the HMD; a secondsensor group comprising at least one sensor providing the HMD to capturea circumjacent image; and a processor configured to control the displayunit, the first sensor group and the second sensor group to acquirefirst sensing information from the first sensor group and second sensinginformation from the second sensor group, wherein the processor isfurther configured to: detect a state of the HMD using at least one ofthe first sensing information and the second sensing information, thestate of the HMD comprising a static state in which an absolute positionof the HMD does not change and a moving state in which the absoluteposition changes; detect, when the state of the HMD is detected as thestatic state, a direction in which a front of the HMD faces based on thefirst sensing information or based on the first sensing information andthe second sensing information; detect, when the state of the HMD isdetected as the moving state, the direction in which the front of theHMD faces based on the second sensing information or based on the secondsensing information and corrected first sensing information; and displayan image of a section of the surrounding image corresponding to thedetected direction, wherein, in detecting the direction in which thefront of the HMD faces based on the second sensing information and thecorrected first sensing information, the processor is further configuredto: correct the acquired first sensing information; and detect thedirection in which the front of the HMD faces using the corrected firstsensing information and the second sensing information.
 2. The HMDaccording to claim 1, wherein the absolute position of the HMD does notsubstantially change in the static state, but substantially changes inthe moving state.
 3. The HMD according to claim 1, wherein the processoris further configured to: detect the state of the HMD as the staticstate when the absolute position of the HMD changes by a distance lessthan or equal to a threshold distance for a predetermined time; anddetect the state of the HMD as the moving state when the absoluteposition of the HMD changes by a distance exceeding the thresholddistance for the predetermined time.
 4. The HMD according to claim 1,wherein, when detecting the state of the HMD using the first sensinginformation, the processor is further configured to acquire the absoluteposition of the HMD as the first sensing information using a globalpositioning system (GPS) sensor belonging to the first sensor group, anddetects the state of the HMD based on the acquired first sensinginformation.
 5. The HMD according to claim 1, wherein, when detectingthe state of the HMD using the second sensing information, the processoris further configured to capture the circumjacent image as the secondsensing information using the second sensor group, process the capturedcircumjacent image, and detect change of the absolute position of theHMD based on a result of the processing.
 6. The HMD according to claim1, further comprising a communication unit configured to transmit andreceive information with an external device, wherein the processor isfurther configured to: acquire travel information of the external deviceusing the communication unit, detect change of the absolute position ofthe HMD using the acquired travel information, and detect the state ofthe HMD based on the detected change of the absolute position of theHMD.
 7. The HMD according to claim 6, wherein the external devicecomprises a means of transportation allowing a user to ride therein. 8.The HMD according to claim 1, wherein, when the state of the HMD isdetected as the moving state, and only the second sensing information isused to detect the direction in which the front of the HMD faces, theprocessor is further configured to: deactivate the first sensor group,and activate the second sensor group or maintain activation of thesecond sensor group.
 9. The HMD according to claim 8, wherein, when thestate of the HMD is detected as the moving state, the processor isfurther configured to additionally detect whether a space containing theHMD is an open space or a closed space using the activated second sensorgroup.
 10. The HMD according to claim 9, wherein the processor isfurther configured to: capture the circumjacent image of the HMD as thesecond sensing information using the activated second sensor group;detect the space containing the HMD as the closed space when thecaptured circumjacent image matches a predetermined image; and detectthe space containing the HMD as the open space when the capturedcircumjacent image does not match the predetermined image.
 11. The HMDaccording to claim 9, wherein the processor is further configured to:set a first reference image using the activated second sensor group upondetecting that the space containing the HMD is the closed space; and seta second reference image using the activated second sensor group upondetecting that the space containing the HMD is the open space.
 12. TheHMD according to claim 11, wherein the processor further configured to:upon detecting that the space containing the HMD is the closed space,capture an image in a first direction using the activated second sensorgroup and set the captured image in the first direction as the firstreference image; and upon detecting that the space containing the HMD isthe open space, capture an image in a second direction using theactivated second sensor group and set the captured image in the seconddirection as the second reference image.
 13. The HMD according to claim11, wherein the first reference image comprises an internal image of thespace containing the HMD and the second reference image comprises a bodyimage of a user wearing the HMD.
 14. The HMD according to claim 11,wherein, upon setting the first reference image or the second referenceimage, the processor is further configured to: capture the circumjacentimage of the HMD as the second sensing information in real time usingthe activated second sensor group; detect the direction in which thefront of the HMD faces by comparing the captured circumjacent image withthe first reference image or the second reference image; and display animage of a section of the circumjacent image corresponding to thedetected direction.
 15. The HMD according claim 1, further comprising acommunication unit configured to transmit and receive information withan external device, wherein, in correcting the first sensinginformation, the processor is further configured to: receive, using thecommunication unit, third sensing information sensed by the externaldevice according to change of an absolute position of the externaldevice; and correct the first sensing information using the receivedthird sensing information.
 16. The HMD according to claim 1, wherein thefirst sensor group comprises at least one of an acceleration sensor, agyro sensor, a geomagnetic sensor, a global positioning system (GPS)sensor, a pressure sensor, an elevation sensor and a proximity sensor.17. The HMD according to claim 1, wherein the second sensor groupcomprises at least one of a camera sensor, an infrared sensor and aproximity sensor.
 18. A method for controlling a head mounted display(HMD) configured to provide a surrounding image, the method comprising:detecting a state of the HMD using at least one of first sensinginformation acquired from a first sensor group comprising at least onesensor configured to sense motion of the HMD and second sensinginformation acquired from a second sensor group comprising at least onesensor configured to capture a circumjacent image, the state of the HMDcomprising a static state in which an absolute position of the HMD doesnot change and a moving state in which the absolute position changes;detecting, when the state of the HMD is detected as the static state, adirection in which a front of the HMD faces based on the first sensinginformation or based on the first sensing information and the secondsensing information detecting, when the state of the HMD is detected asthe moving state, the direction in which the front of the HMD facesbased on the second sensing information or based on the second sensinginformation and corrected first sensing information; and displaying animage of a section of the surrounding image corresponding to thedetected direction, wherein, in detecting the direction in which thefront of the HMD faces based on the second sensing information and thecorrected first sensing information, the method further comprises:correcting the acquired first sensing information; and detecting thedirection in which the front of the HMD faces using the corrected firstsensing information and the second sensing information.
 19. The methodaccording to claim 18, wherein the detecting of the state of the HMDcomprises: detecting the state of the HMD as the static state when theabsolute position of the HMD changes by a distance less than or equal toa threshold distance for a predetermined time; and detecting the stateof the HMD as the moving state when the absolute position of the HMDchanges by a distance exceeding the threshold distance for thepredetermined time.